This invention relates to non-woven webs of polyester fibers and their processing. More particularly it relates to non-woven fabrics suitable for use in the manufacture of folding window blinds, such fabric being embossed to present a woven appearance and laminated with a metalized polyester film if opacity is required. The fabrics formed by this process are particularly suited for use in fabricating honeycomb insulating material as disclosed in U.S. Pat. No. 4,450,027, May 22, 1984 to Colson.
Such fabrics generally have been formed by embossing a woven pattern onto the surface of a spunbonded polyester substrate web. The substrate is saturated with a binder material to fill the interstices between the polyester fibers, completing the woven appearance and rendering the fabric impervious to adhesives used in latter fabrication steps. There are two types of spunbonded web which may be used to make this fabric: a binder bonded type and a thermally bonded type. The thermally bonded type is formed by extruding together two different polyester fibers, a highmelt and a lowmelt fiber. The web is then heated to the melting point of the lowmelt fibers which bond to the highmelt fibers, holding the web together. Embossing and adding binder may be done in later processing steps. In the binder bonded type only highmelt fibers are extruded onto a belt. The fibers are then embossed and subsequently saturated with a binder material which holds the fibers together to form the web.
The thermally bonded type of spunbonded polyester web exhibits discontinuities in thickness which repeat at least every four to five inches in both the lateral and longitudinal directions. These thickness discontinuities are resolved to some extent in the embossing process when the substrate is run through the embossing rollers under high temperature and pressure. However, in prior art methods the spunbonded web is generally processed in widths ranging from 30 to 180 inches, therefore the web is not embossed uniformly in the lateral direction because thick spots in the web prevent full pressure from being applied to adjacent thin spots. This problem has been alleviated to a degree by pairing the steel embossing roller with a resilient rubber roller to compensate for the lateral discontinuities. However, embossers using rubber rollers do not provide as high a quality emboss as do these with all steel rollers.
In prior art processes the application of a metalized polyester blackout film in order to make the fabric opaque required a number of separate steps that are time consuming and costly. The metalized polyester film is formed by vacuum metalizing a polyester film with an aluminum base material. This metalization corrodes easily and must be "topcoated" with a material to prevent corrosion. Topcoating generally is done with a thin, clear material layered over the metal. This thin, clear topcoat, however, is expensive and difficult to apply, adding significantly to the total cost of the material.
The metalized blackout film as prepared above is then bonded to the spunbonded substrate web in a separate process. Generally this bonding process involves the application of an adhesive to the substrate, drawing that adhesive through a drying tunnel, and then mating the substrate, with the sticky dried adhesive, to the film layer under heat and pressure.
Although the non-woven fabrics produced generally as described above are suitable for applications in the manufacture of folding window blinds they are costly to produce due to expensive materials and critical processing steps. It is therefore desirable to develop a non-woven fabric which would exhibit the same qualities of woven appearance and complete opacity while reducing the expense and difficulty of manufacture.